The present invention relates to a positive photoresist composition for far ultraviolet exposure, which is used in the ultramicro-lithography process and other photofabrication processes, such as production of ultra-LSI and high-capacitance micro-chip. More specifically, the present invention relates to a positive photoresist composition for far ultraviolet exposure, which can form a highly precise pattern using light in the far ultraviolet region including an excimer laser ray, particularly, in the region of 250 nm or less.
In recent years, the integration degree of integrated circuits is more and more elevated and in the production of a semiconductor substrate such as ultra-LSI, working to provide an ultrafine pattern consisting of lines having a width of half micron or less is required. To meet this requirement, the wavelength used in the exposure apparatus for photolithography increasingly becomes shorter and at the present time, studies are being made on the use of an excimer laser ray (e.g., XeCl, KrF, ArF) having a short wavelength among far ultraviolet rays.
In the formation of a pattern for lithography using this wavelength region, a chemical amplification-system resist is used.
The chemical amplification-system resist in general can be roughly classified into three groups, that is, commonly called 2-component system, 2.5-component system and 3-component system. The 2-component system uses a combination of a compound capable of generating an acid by the photochemical decomposition (hereinafter referred to as a xe2x80x9cphoto-acid generatorxe2x80x9d) and a binder resin. This binder resin is a resin having within the molecule a group capable of decomposing by the action of an acid and thereby increasing solubility of the resin in an alkali developer (also called acid-decomposable group) The 2.5-component system contains a low molecular compound having an acid-decomposable group in addition to the 2-component system. The 3-component system contains a photo-acid generator, an alkali-soluble resin and the above-described low molecular compound.
The chemical amplification-system resist is suitable as a photoresist used under irradiation of an ultraviolet ray or a far ultraviolet ray but still in need of coping with the characteristics required for individual uses.
As a photoresist composition for use with an ArF light source, a resin in which an alicyclic hydrocarbon site is introduced so as to impart dry etching resistance has been proposed. However, the alicyclic hydrocarbon site introduced disadvantageously renders the system to be extremely hydrophobic, and as a result, the resist can not be developed with an aqueous tetramethylammonium hydroxide (hereinafter referred to as xe2x80x9cTMAHxe2x80x9d) solution heretofore widely used as a developer for resists or there may arise a phenomenon such that the resist falls off from the substrate during the development.
With an attempt to overcome this hydrophobitization of the resist, an organic solvent such as isopropyl alcohol is mixed in the developer. This gains a certain result but still suffers from problems such as swelling of the resist film or the cumbersome process. From the standpoint of improving the resist, a large number of techniques have been proposed, for example, hydrophobitization ascribable to various alicyclic hydrocarbon sites is compensated for by introducing a hydrophilic group.
JP-A-10-10739 (the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d) discloses an energy-sensitive resist material containing a polymer obtained by polymerizing a monomer having an alicyclic structure such as norbornene ring in the main chain, a maleic acid anhydride and a monomer having a carboxyl group. JP-A-10-111569 discloses a radiation-sensitive resin composition containing a resin having an alicyclic skeleton in the main chain and a radiation-sensitive acid-generating agent. JP-A-11-202491 discloses a radiation-sensitive resin composition containing a polymer having a norbornene derivative and an androstane-17-carboxylic acid ester compound.
The resin having an acid-decomposable group, which is used in the photoresist for far ultraviolet exposure, generally contains an aliphatic cyclic hydrocarbon group within the molecule at the same-time. Therefore, the resin becomes hydrophobic and there arise problems attributable to it. For overcoming the problems, various techniques have been aggressively investigated as described above, however, these techniques are still insufficient in many points (particularly in the developability) and in need of improvements.
On the other hand, JP-A-8-248561 discloses a photoreactive composition comprising a photo-acid generator and an acid-increasing agent capable of generating a new acid by the acid generated from the acid-generating agent. In SPIE., vol. 3049, pp. 76-82, a chemical amplification-system resist for 193-nm lithography containing an acid-generating agent, a partially protected alicyclic polymer and an acid-increasing agent is disclosed.
However, this technique using a light source of emitting a far ultraviolet ray of short wavelength, for example, an ArF excimer laser (193 nm), as the exposure light source is still in need of improvements in view of the developability. To speak specifically, development defect may arise or scum (development residue) may be generated. Furthermore, the line width fluctuates every each pattern formation and improvement are necessary also in the line width reproducibility.
The defocus latitude depended on line pitch is also in need of improvements. More specifically, a device has a portion where lines are crowded, a pattern where the space is broad as compared with lines, and isolated lines. Therefore, it is important to resolve various lines with high reproducibility. However, reproduction of various lines cannot be easily attained because of optical factors and the resist is not yet succeeded in undertaking the part of solving this problem at present. In particular, the above-described resist system containing an alicyclic group conspicuously varies in the reproducibility between the isolated pattern and the crowded pattern, and improvements are being demanded.
In addition, the storage stability of the resist solution is also in need of improvements. For example, when a chemical amplification-system photoresist is stored in the liquid state, due to the poor compatibility between the resin and the photo-acid generator, particles may be generated in the solution or the resist performance may be deteriorated (deterioration in the storage stability of the resist solution).
JP-A-10-254139 discloses a resin composition containing a solvent comprising a mixture of a resin having an acid-decomposable group and an alicyclic skeleton, a radiation-sensitive acid-generating agent and at least one selected from the group consisting of linear ketone, cyclic ketone, propylene glycol monoalkyl ether acetate and alkyl 2-hydroxypropionate. This system also has the above-described problem of poor storage stability and studies are being made by the similar approach.
Accordingly, an object of the present invention is to attain technical improvements in the capability inherent in the microphotofabrication using a far ultraviolet ray, particularly an ArF excimer laser ray.
More specifically, a first object of the present invention is to provide a positive photoresist composition free from the generation of development defect and scum at the development, and a positive photoresist composition for far ultraviolet exposure, having excellent line width reproducibility.
A second object of the present invention is to provide a positive photoresist composition excellent in the sensitivity, resolution, dry etching resistance and adhesion to the substrate, and free from the generation of development defect and scum at the development and a positive photoresist composition for far ultraviolet exposure, having excellent defocus latitude depended on line pitch.
A third object of the present invention is to provide a positive photoresist composition having excellent aging storage stability and free of the generation of development defect at the development.
As a result of extensive investigations on the constituent materials of a photoresist in the positive chemical amplification system, the present inventors have found that the above-described objects of the present invention can be attained by using a specific acid-decomposable resin and a specific additive. The present invention has been accomplished based on this finding.
Namely, the above-described objects can be attained by the following constructions.
(1) A positive photoresist composition for far ultraviolet exposure as a first aspect of the present invention to achieve the first object, comprising (A) a compound capable of generating an acid by the irradiation of an actinic ray or radiation, (B) a polymer having at least either a repeating unit represented by the following formula (Ia) or a repeating unit represented by the following formula (Ib) and a repeating unit represented by the following formula (II) and having a group capable of decomposing by the action of an acid, and (C) a compound capable of decomposing by the action of an acid to generate a sulfonic acid: 
wherein
in formula (Ia), R1 and R2 each independently xe2x80x94COOH, xe2x80x94COOR5, xe2x80x94COxe2x80x94NHxe2x80x94R6, xe2x80x94COxe2x80x94NHxe2x80x94SO2xe2x80x94R6 (wherein R5 represents an alkyl group which may have a substituent, a cyclic hydrocarbon group which may have a substituent or a xe2x80x94Y group shown below, and R6 represents an alkyl group which may have a substituent or a cyclic hydrocarbon group which may have a substituent), an alkyl group which may be substituted, an alkoxy group which may be substituted, a cyclic hydrocarbon group which may be substituted or a xe2x80x94Y group shown below, X represents oxygen atom, sulfur atom, xe2x80x94NHxe2x80x94, xe2x80x94NHSO2xe2x80x94 or xe2x80x94NHSO2NHxe2x80x94, and A represents a single bond or a divalent linking group:
xe2x80x94Y group: 
(wherein R21 to R30 each independently represents hydrogen atom or an alkyl group which may have a substituent, and a and b each represents 1 or 2);
in formula (Ib), Z2 represents xe2x80x94Oxe2x80x94 or xe2x80x94N(R3)xe2x80x94 (wherein R3 represents hydrogen atom, a hydroxyl group or xe2x80x94OSO2xe2x80x94R4 (wherein R4 represents an alkyl group, a haloalkyl group, a cycloalkyl group or a camphor residue)); and
in formula (II), R11 and R12 each independently represents hydrogen atom, a cyano group, a halogen atom or an alkyl group which may have a substituent, and Z1 represents an atomic group necessary for forming an alicyclic structure which contains two bonded carbon atoms (Cxe2x80x94C) and may have a substituent;
(2) the positive photoresist composition for far ultraviolet exposure as described in (1) above, wherein Z1 in formula (II) represents an atomic group necessary for forming a bridged alicyclic structure which contains two bonded carbon atoms (Cxe2x80x94C) and may have a substituent;
(3) the positive photoresist composition for far ultraviolet exposure as described in (1) above, wherein formula (II) is the following formula (II-A) or (II-B): 
wherein R13 to R16 each independently represents hydrogen atom, a halogen atom, a cyano group, xe2x80x94COOH, xe2x80x94COOR5 (wherein R5 is the same as defined above), a group capable of decomposing by the action of an acid, xe2x80x94C(xe2x95x90O)xe2x80x94Xxe2x80x94Axe2x80x94R17 (wherein X and A are the same as defined above, and R17 represents xe2x80x94COOH, xe2x80x94COOR5, xe2x80x94CN, a hydroxyl group, an alkoxy group which may have a substituent, xe2x80x94COxe2x80x94NHxe2x80x94R6, xe2x80x94COxe2x80x94NHxe2x80x94SO2xe2x80x94R6 (wherein R5 and R6 are the same as defined above) or a xe2x80x94Y group shown above), an alkyl group which may have a substituent or a cyclic hydrocarbon group which may have a substituent, at least two of R13 to R16 may be combined to form a ring, and n represents 0 or 1;
(4) a positive photoresist composition for far ultraviolet exposure as a second aspect to achieve the second object, comprising (A) a compound capable of generating an acid by the irradiation of an actinic ray or radiation, (B) a polymer having at least either a repeating unit represented by the following formula (Ia) or a repeating unit represented by the following formula (Ib) and a repeating unit represented by formula (II) and having a group capable of decomposing by the action of an acid, and (D) a fluorine-type and/or silicon-type surface active agent;
(5) the positive photoresist composition for far ultraviolet exposure as described in (4) above, wherein Z1 in formula (II) represents an atomic group necessary for forming a bridged alicyclic structure which contains two bonded carbon atoms (Cxe2x80x94C) and may have a substituent;
(6) the positive photoresist composition for far ultraviolet exposure as described in (4) above, wherein formula (II) is formula (II-A) or (II-B);
(7) the positive photoresist composition for far ultraviolet exposure as described in any one of (4) to (6) above, which contains a nitrogen-containing basic compound; and
(8) the positive photoresist composition for far ultraviolet exposure as described in (7) above, wherein the nitrogen containing basic compound is at least one compound selected from the group consisting of 1,5-diazabicyclo[4.3.0]-5-none, 1,8-diazabicyclo[5.4.0]-7-undecene, 1,4-diazabicyclo[2.2.2]octane, 4-dimethylaminopyridine, hexamethylenetetramine, 4,4-dimethylimidazoline, pyrroles, pyrazoles, imidazoles, pyridazines, pyrimidines, tertiary morpholines and hindered amines having a hindered piperidine skeleton.
Furthermore, as a result of extensive investigations on the constituent materials of a photoresist in the positive chemical amplification system, the present inventors have found that the objects of the present invention can be attained by using a specific acid-decomposable resin and a specific mixed solvent. The present invention has been accomplished based on this finding.
Namely, the above-described objects can be attained by the following constructions as a third aspect to achieve the third object.
(9) a positive photoresist composition for far ultraviolet exposure, comprising (A) a compound capable of generating an acid by the irradiation of an actinic ray or radiation, (B) a polymer having at least either a repeating unit represented by the following formula (Ia) or a repeating unit represented by the following formula (Ib) and a repeating unit represented by formula (II) and having a group capable of decomposing by the action of an acid, and (E) a mixed solvent containing at least one selected from the group consisting of butyl acetate and propylene glycol monoalkyl ether carboxylate and at least one selected from the group consisting of ethyl lactate and propylene glycol monoalkyl ether;
(10) the positive photoresist composition for far ultraviolet exposure as described in (9) above, wherein Z1 in formula (II) represents an atomic group necessary for forming a bridged alicyclic structure which contains two bonded carbon atoms (Cxe2x80x94C) and may have a substituent;
(11) the positive photoresist composition for far ultraviolet exposure as described in (9) above, wherein formula (II) is formula (II-A) or (II-B);
(12) the positive photoresist composition for far ultraviolet exposure as described in any one of (9) to (11) above, which contains a nitrogen-containing basic compound;
(13) the positive photoresist composition for far ultraviolet exposure as described in (12) above, wherein the nitrogen containing basic compound is at least one compound selected from the group consisting of 1,5-diazabicyclo[4.3.0]-5-none, 1,8-diazabicyclo[5.4.0]-7-undecene, 1,4-diazabicyclo[2.2.2]octane, 4-dimethylaminopyridine, hexamethylenetetramine, 4,4-dimethylimidazoline, pyrroles, pyrazoles, imidazoles, pyridazines, pyrimidines, tertiary morpholines and hindered amines having a hindered piperidine skeleton; and
(14) the positive photoresist composition as described in any one of (9) to (13) above, wherein the mixed solvent (E) additionally contains at least one solvent selected from the group consisting of xcex3-butyrolactone, ethylene carbonate and propylene carbonate.